Synchronous drive system and method of making the same

ABSTRACT

The combination of a toothed pulley and a toothed belt and method of making the same are provided. The toothed belt has teeth that serially mesh with cavities of the pulley that are respectively disposed between adjacent teeth thereof. Each pulley cavity has a longitudinal substantially trapezoidal cross-sectional configuration. Each belt tooth has a longitudinal cross-sectional configuration that defines a pair of spaced side faces that respectively has free end portions that are remote from adjacent roots thereof and that are spaced apart from each other by a bottom face of the tooth. The teeth of the pulley and the belt are so constructed and arranged that each belt tooth would have the pair of spaced apart free end portions thereof compressed radially outwardly and inwardly toward each other by the respective adjacent pulley teeth if that belt tooth is fully received in the cavity between those respective adjacent pulley teeth and those respective adjacent pulley teeth are just making contact with the land areas of the belt on each side of that belt tooth while being spaced from the respective roots of that belt tooth.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional patent application of its copendingparent patent application, Ser. No. 883,257, filed July 8, 1986, nowU.S. Pat. No. 4,679,999, which, in turn, is a continuation patentapplication of its copending parent patent application, Ser. No.671,392, filed Nov. 15, 1984, now abandoned in favor of its continuationapplication, this application also being related to copending patentapplication, Ser. No. 827,999, filed Feb. 10, 1986, now U.S. Pat. No.4,650,443 which, in turn, is a divisional patent application of saidSer. No. 671,392.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved synchronous belt and pulley drivesystem and to a method of making such a drive system.

2. Prior Art Statement

It is known to provide the combination of a toothed pulley and a toothedbelt that has the teeth thereof serially mesh with cavities of thepulley that are respectively disposed between adjacent teeth thereof,each belt tooth having a longitudinal cross-sectional configuration thatdefines a pair of spaced side face means that respectively have free endportions thereof that are remote from adjacent root means thereof. Forexample, see the U.S. Pat. Nos. 3,756,091 to Miller and 3,404,576 toCicognani et al.

It is also known to provide a non-conjugate action of the belt teethwith the pulley teeth to decrease contact stress. For example, see theU.S. Pat. Nos. 2,987,932 to Szonn; 3,026,737 to Berg; 3,968,701 toMaruxama; 4,007,644 to Weinberger and 4,148,225 to Redmond, Jr. et al.

SUMMARY OF THE INVENTION

It is one feature of this invention to provide a combination of atoothed pulley and a toothed belt which relieves the high sheer stressat the roots of the belt teeth as well as reduces land area slapping.

In particular, it was found according to the teachings of this inventionthat the belt teeth and the pulley teeth of a synchronous drive systemcould be so constructed and arranged that the free end portions of eachbelt tooth could be compressed radially outwardly and inwardly towardeach other by the respective adjacent pulley teeth before those adjacentpulley teeth make contact with the land areas of the belt on each sideof that belt tooth while being spaced from the respective root means ofthat belt tooth whereby the resulting pre-stressing and trapping of thatbelt tooth by those adjacent pulley teeth maintain that belt tooth inthe pulley groove in a manner that is believed to reduce land wear andthereby extend the life of the belt.

For example, one embodiment of this invention provides the combinationof a toothed pulley and a toothed belt that has the teeth thereofserially mesh with cavities of the pulley that are respectively disposedbetween adjacent teeth thereof, each pulley cavity having a longitudinalsubstantially trapezoidal cross-sectional configuration, each belt toothhaving a longitudinal cross-sectional configuration that defines a pairof spaced side face means that respectively have free end portionsthereof that are remote from adjacent root means thereof. The teeth ofthe pulley and the belt are so constructed and arranged that each belttooth would have the pair of free end portions thereof compressedradially outwardly and inwardly toward each other by their respectiveadjacent pulley teeth if that belt tooth is fully received in the cavitybetween those respective adjacent pulley teeth and those respectiveadjacent pulley teeth are just making contact with the land areas of thebelt on each side of that belt tooth while being spaced from therespective root means of that belt tooth.

Accordingly, it is an object of this invention to provide an improvedcombination of a toothed pulley and a toothed belt that has the teeththereof serially mesh with cavities of the pulley that are respectivelydisposed between adjacent teeth thereof, the combination of thisinvention having one or more of the novel features of this invention asset forth above or hereinafter shown or described.

Another object of this invention is to provide a method of making thecombination of a toothed pulley and a toothed belt that has the teeththereof serially mesh with cavities of the pulley that are respectivelydisposed between adjacent teeth thereof, the method of this inventionhaving one or more of the novel features of this invention as set forthabove or hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating the synchronous drive system ofthis invention.

FIG. 2 is an enlarged fragmentary perspective view illustrating theimproved belt of the drive system of FIG. 1.

FIG. 3 is an enlarged fragmentary cross-sectional view taken on line3--3 of FIG. 2.

FIG. 4 is a fragmentary schematic cross-sectional view illustrating oneof the teeth of the belt of this invention as it initially enters thecavity between a pair of pulley teeth of the pulley of the systemillustrated in FIG. 1.

FIG. 5 is a view similar to FIG. 4 and illustrates a further movementbetween the belt tooth of FIG. 4 and the pulley teeth of FIG. 4.

FIG. 6 is a view similar to FIG. 4 and illustrates the theoreticalpre-stressing of the belt tooth of FIG. 4 if that belt tooth of FIG. 4is fully received into the cavity defined by the two pulley teeth withthose two pulley teeth just making contact with the land areas onopposite sides of that belt tooth while being spaced from the root meansof the belt tooth.

FIG. 7 is a view similar to FIG. 4 and illustrates another embodiment ofthis invention.

FIG. 8 is a view similar to FIG. 6 with the embodiment of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as providing a synchronous drive system wherein the beltteeth are each substantially trapezoidal in their longitudinalcross-sectional configurations and the pulley teeth are substantiallycurvilinear in their longitudinal cross-sectional configurations, it isto be understood that the various features of this invention can beutilized singly or in any combination thereof to provide a synchronousdrive system wherein the belt teeth and/or the pulley teeth havedifferent longitudinal cross-sectional configurations while stillproviding the improved features of this invention.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIG. 1, the improved synchronous drive system orcombination of a toothed pulley and a toothed belt that has the teeththereof serially mesh with cavities of the pulley that are respectivelydisposed between adjacent teeth thereof is generally indicated by thereference numeral 20 and comprises a pair of toothed pulleys 21 and 22and an endless toothed belt 23 cooperating therewith to transmit adriving relation between the pulleys 21 and 22 in a manner that issubstantially conventional in the art, except for the improved featuresof this invention as hereinafter set forth, and such an arrangement isgenerally set forth in the aforementioned seven U.S. Pat. Nos.3,756,091; 3,404,576; 2,987,932; 3,026,737; 3,968,701; 4,007,644 and4,148,225 whereby these seven U.S. Patents are all being incorporatedinto this disclosure by this reference thereto.

The pulleys 21 and 22 can be formed of any suitable material, such asmetallic material, and differ from each other in that the effectivediameters thereof are different whereby the number of teeth thereon arelikewise different but the overall configuration of the teeth thereofare basically the same.

However, it is to be understood that the configuration of the teeth ofthe pulleys 21 and 22 could be different as long as at least one of thepulleys 21 or 22 has the teeth thereof perform the inventive features ofthis invention with the belt 23 as hereinafter set forth.

Accordingly, reference is now made to FIGS. 4, 5 and 6 wherein it can beseen that the pulley 21 (and/or pulley 22) has a plurality ofsubstantially curvilinear pulley teeth 24 extending around the peripherythereof with each pair of adjacent teeth 24 defining a cavitytherebetween that is generally indicated by the reference numeral 25.The longitudinal cross-sectional configurations of the pulley teeth 24define facing curvilinear side face means 26 that define the cavity 25therebetween with the side face means 26 of adjacent pulley teeth 24joining together at the bottom 27 of the cavity 25 as illustrated inFIG. 4 and joining with other side face means 26 to define outer tips 28of the pulley teeth 24 that are also substantially curvilinear.

As previously stated, the longitudinal cross-sectional configuration ofthe pulley teeth 24 can be any suitable configuration which will producethe improved results of this invention as hereinafter set forth.However, in the embodiment illustrated in FIGS. 4-6, the configurationof the pulley teeth 24 and, thus, of the pulley 21 is substantially thesame as the pulley illustrated in FIG. 3 of the aforementioned U.S.Patent to Miller, U.S. Pat. No. 3,756,091 whereby further details of thepulley 21 need not be set forth.

The belt 23 of this invention is best illustrated in FIGS. 2 and 3 andcomprises a conventional tensile means 30 having a plurality of teeth 31extending from the inner side 32 thereof and a backing member 33extending from the outer side 34 thereof, the teeth 31 and backingmember 33 being mainly formed from any suitable fiber loaded or unloadedpolymeric material or materials and being formed in any suitable manner,such as in the manner set forth in the U.S. Pat. Nos. 3,078,026, toSkura, 4,343,666, to Wentzel, the co-pending U.S. Patent Application ofMarsh et al, Ser. No. 502,777, filed June 9, 1983, now U.S. Pat. No.4,504,342, the co-pending U.S. patent application of Wetzel et al, Ser.No. 658,832, filed Oct. 9, 1984, now U.S. Pat. No. 4,617,079, thecopending U.S. patent application of Whitt, Ser. No. 659,159, filed Oct.9, 1984, now U.S. Pat. 4,626,232, etc., whereby these two U.S. Patentsand three U.S. co-pending Patent Applications are all being incorporatedinto this disclosure by this reference thereof.

Therefore, it can be seen that the particular method of making the beltconstruction 23 of this invention is not to be a limitation on thisinvention as this invention is direction to the feature of forming thebelt teeth 31 and the pulley teeth 24 to cooperate in a unique manner ashereinafter set forth.

If desired, a conventional fabric layer 35 can cover the outer surfaceof the teeth 31 as well as the land areas 36 of the belt 23 that aredisposed between adjacent teeth 31 in a conventional manner.

Each belt tooth 31 has a longitudinal cross-sectional configuration thatis substantially trapezoidal and defines opposed side face means 37 thatrespectively join with a substantially flat bottom face means 38 andsubstantially curvilinear root means 39, each side face 37 having asubstantially flat or straight section 40 and an arcuate section 41 withthe arcuate section 41 being defined by a radius 42 having its center 43disposed intermediate the opposed side face means 37 of the respectivetooth 31. Each arcuate root means 39 of each belt tooth 31 is defined bya radius 44 having its center 45 disposed outboard of the respectiveside face means 37. The flat section 40 of each side face means 37 ofeach belt tooth 31 join with its respective arcuate root means 39 andwith its arcuate section 41 while that arcuate section 41 joins with theflat bottom face means 38, the flat section 40 of each side face means37 being disposed at an angle 46 relative to a line 47 which issubstantially parallel to the transverse center line 48 of thatrespective belt tooth 31.

The arcuate section 41 of each side face means 37 of each belt tooth 31defines at least part of a free end portion or corner means of the belttooth 31 that is generally indicated by the reference numeral 49 and isdisposed remote from the respective root means 39 of that belt tooth 31.

The size of the belt teeth 31 relative to the cavities 25 of the pulley21 (and/or pulley 22) is so selected that when a particular belt tooth31 of the belt 23 as illustrated in FIG. 4 is initially received in thecavity 25 between an adjacent pair of pulley teeth 24, which the pulley21 and belt 23 both rotating in a counterclockwise direction in FIG. 4,the left-hand land means 36 of the belt 23 makes contact with the tip 28of the left-hand pulley tooth 24 while the corner means 49 of that belttooth 31 initially and respectively make contact with the opposed sidefaces 26 of the adjacent belt teeth 24.

At this time, it can be seen that a relatively wide gap or area 50 isprovided between the left-hand root means 39 of that belt tooth 31 andthe adjacent surface or face means 26 of the left-hand pulley tooth 24so that no stress is being placed on that root means 39.

Further rotation of the pulley means 21 and belt means 23 in acounterclockwise direction from the position illustrated in FIG. 4 tothe position illustrated in FIG. 5 causes the tooth 31 to be compresedin the left-hand corner means 49 thereof, as represented by thedash-dotted line 51 in FIG. 5, before the left-hand root means 39 makescontact with the side face means 26 of the left-hand tooth 24, the line51 being the normal outline profile of the belt tooth 31. In thismanner, the left-hand corner means 49 of the belt tooth 31 is compressedradially outwardly and inwardly to the right by the amount representedby the area 52 in FIG. 5 that is bordered by the line 51 and the sideface means 26 of the left-hand tooth 24 as illustrated in FIG. 5 andthis compression takes up a considerable force in the belt tooth 31 at apoint therein that is remote from the left-hand root means 39 before anyforce would be placed on the left-hand root area 39 of the belt 23.

It is believed that providing such compression area 52 in the belt tooth31 remote from its respective root means 39 enhances the life of thebelt means 23 by removing as much stress or strain in the root areas 39of the belt teeth 31 as possible during their driving or drivenoperation with the pulley 21.

The configurations and arrangement of the belt teeth 31 and pulley teeth24 are such that if the respective belt tooth 31 could be theorecticallyfully and uniformly received in the cavity 25 between the adjacentpulley teeth 24 in the manner illustrated in FIG. 6, the corner means 49of the belt tooth 31 would be radially outwardly and inwardly compressedtoward each other by the amount represented by the areas 53 in FIG. 6that is bounded by the surface means 26 of the adjacent pulley teeth 24and the normal profile outline of the belt tooth 31 represented by thedash-dotted lines 54 in FIG. 6 at the time the pulley teeth 24 have thetips 28 thereof just engaging the adjacent land areas 36 of the belt 23on each side of that belt tooth 31 while the side face means 26 of theadjacent pulley teeth 24 are respectively spaced from the adjacent rootmeans 39 of the belt tooth 31 by the large gaps 50' illustrated in FIG.6 whereby theoretically no force or stress is being imposed on the rootmeans 39 or land areas 36 at this time.

In this manner, it can be seen that each belt tooth 31 of the belt 23 ofthis invention cooperates with its receiving cavity 25 between adjacentpulley teeth 24 by having both of the corner means 49 thereof compressedradially outwardly and inwardly toward each other through the trappingeffect of the side face means 26 of the adjacent pulley teeth 24 whichproduces both a radial and horizontal pre-stressing of the belt tooth 31before the root means 39 and land areas 36 of the belt 23 aresubsequently stressed by further action between the respective belttooth 31 and pulley teeth 24 through the normal work load being imposedthereon and it is believed that this pre-stressing effect results inincreased belt life and reduced noise by relieving the high shear stressat the root means 39 of each belt tooth 31 and a reduced land areaslapping by the land areas 36 engaging the tips 28 of the teeth 24.

While this invention is not to be limited to any particularconfigurations or dimensions, one belt 23 of this invention that hasbeen utilized in pulleys 21 and 22 formed similar to the aforementionedU.S. Patent to Miller, U.S. Pat. No. 3,756,091, wherein generally theradius of curvature of each cavity 25 is approximately 0.103 of an inchand the cavity depth is approximately 0.142 of an inch, had the pitch ofthe belt teeth 31 thereof approximately 0.31496 of an inch, the numberof belt teeth being 120, the belt pitch length being approximately37.795275 inches and the belt pitch diameter being approximately12,030609 inches. The belt teeth 31 of such belt 23 each had an overallheight along the center line 48 from the bottom surface face 38 toapproximately the inner side 32 of the tensile means 30 of approximately0.130 of an inch with the distance between the corner means 49 thereofbeing approximately 0.182 of an inch, each radius 42 thereof beingapproximately 0.060 of an inch, each radius 44 thereof beingapproximately 0.031 of an inch and the flat sections 40 thereof makingan included angle of approximately 9°.

Such a belt provided the gross interference during engagement with thepulley as previously described and this actually increased belt life aswell as provided a quieter drive system. For example, the prior knownbelt for such system had a belt life of approximately 122.7 hourswhereas the life of the belt 23 of this invention was approximately193.6 hours.

As previously stated, the particular configurations of the pulley teeth24 and belt teeth 31 cooperating therewith in the unique manner providedby this invention can be provided by other configurations than thoseillustrated in the drawings and previously described.

For example, reference is now made to FIGS. 7 and 8 wherein anothersynchronous drive system of this invention is generally indicated by thereference numeral 20A and parts thereof similar to the drive system 20previously described are indicated by like reference numerals followedby the reference letter "A."

As illustrated in FIGS. 7 and 8, the pulley 21A has the teeth 24Athereof so constructed and arranged that the same provide asubstantially trapezoidal cavity 25A between adjacent pulley teeth 24Athat is defined by substantially flat side face means 26A even thoughthe tips 28A of the teeth 24A are rounded as illustrated. However, thebottom 27A of each cavity 25A is substantially flat as illustrated.

In contrast, the longitudinal cross-sectional configuration of each belttooth 31A of the belt 32A of this invention is substantially the same asthe configurations set forth in FIG. 2 of the aforementioned U. S.Patent to Miller, U.S. Pat. No. 3,756,091 and would theoretically havethe opposed free end portions 43A of the opposed side face means 37Athereof compressed radially outwardly and inwardly toward each other bythe amount of areas 53A represented in FIG. 8 as the area bordered bythe side faces 26A of the pulley teeth 24A and the dash-dotted lines 54Athat depict the normal profile of the tooth 31A when that tooth 31A isfully and uniformly received in the cavity 25A and has the tips 28A ofthe pulley teeth 24A just engaging the land areas 36A on each side ofthat tooth 31A as illustrated in FIG. 8. At this time, it can be seen inFIG. 8 that the root means 39A of the belt tooth 31A are fully spacedfrom the sides 26A of the adjacent pulley teeth 24A in the same manneras the root means 39 of the teeth 31 in the cavities 25 as previouslydescribed whereby it is believed the belt 23A and pulley 21A willfunction in the manner previously set forth to extend the life of thebelt 23A through prestressing thereof as well as reduce the noise ofoperation thereof through reduced land slapping thereof.

Therefore, it can be seen that this invention not only provides animproved synchronous drive system or combination of a toothed pulley anda toothed belt, but also this invention provides an improved method ofmaking such a drive system or combination.

While the forms and methods of the invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the apprended claims wherein each claim setsforth what is believed to be known in each claim prior to this inventionin the portion of each claim that is disposed before the terms "theimprovement" and sets forth what is believed to be new in each claimaccording to this invention in the portion of each claim that isdisposed after the terms "the improvement" whereby it is believed thateach claim sets forth a novel, useful and unobvious invention within thepurview of the Patent Statute.

What is claimed is:
 1. In the combination of a toothed pulley and atoothed belt that has the teeth thereof serially mesh with cavities ofsaid pulley that are respectively disposed between adjacent teeththereof, each pulley cavity having a longitudinal substantiallytrapezoidal cross-sectional configuration, each belt tooth having alongitudinal cross-sectional configuration that defines a pair of spacedside face means that respectively have free end portions thereof thatare remote from adjacent root means thereof, the improvement whereinsaid teeth of said pulley and said belt are so constructed and arrangedthat each belt tooth would have said pair of free end portions thereofcompressed radially outwardly and inwardly toward each other by therespective adjacent pulley teeth if that belt tooth is fully received inthe cavity between thsoe respective adjacent pulley teeth and thoserespective adjacent pulley teeth are just making contact with the landareas of the belt on each side of that belt tooth while being spacedfrom the respective root means of that belt tooth.
 2. The combination asset forth in claim 1 wherein each belt tooth is substantiallycurvilinear.
 3. The combination as set forth in claim 1 wherein eachpulley cavity has a bottom and each belt tooth has a bottom face meansprovided with a center thereof that is spaced from the bottom of itsrespective pulley cavity if that belt tooth is fully received in thatrespective pulley cavity between its respective adjacent pulley teethand those respective adjacent pulley teeth are just making contact withthe land areas of the belt on each side of that belt tooth while beingspaced from the respective root means of that belt tooth.
 4. Thecombination as set forth in claim 3 wherein each belt tooth issubstantially curvilinear.
 5. In the method of making the combination ofa toothed pulley and a toothed belt that has the teeth thereof seriallymesh with cavities of said pulley that are respectively disposed betweenadjacent teeth thereof, each pulley cavity having a longitudinalsubstantially trapezoidal cross-sectional configuration, each belt toothhaving a longitudinal cross-sectional configuration that defines a pairof spaced side face means that respectively have free end portionsthereof that are remote from adjacent root means thereof, theimprovement comprising the step of forming said teeth of said pulley andsaid belt to be so constructed and arranged that each belt tooth wouldhave said pair of free end portions thereof compressed radiallyoutwardly and inwardly toward each other by the respective adjacentpulley teeth if that belt tooth is fully received in the cavity betweenthose respective adjacent pulley teeth and those respective adjacentpulley teeth are just making contact with the land areas of the belt oneach side of that belt tooth while being spaced from the respective rootmeans of that belt tooth.
 6. The method as set forth in claim 5 andincluding the step of forming each belt tooth to be substantiallycurvilinear.
 7. The method as set forth in claim 5 and including thestep of forming each pulley cavity to have a bottom and each belt toothto have a bottom face means provided with a center thereof that isspaced from the bottom of its respective pulley cavity if that belttooth is fully received in that respective pulley cavity between itsrespective adjacent pulley teeth and those respective adjacent pulleyteeth are just making contact with the land areas of the belt on eachside of that belt tooth while being spaced from the respective rootmeans of that belt tooth.
 8. The method as set forth in claim 7 andincluding the step of forming each belt tooth to be substantiallycurvilinear.